Achondroplasia (ACh) is the most frequent bone dysplasia. The mode of inheritance is autosomal dominant. The incident of neurological complications ranges between 20% and 47%; frequently the symptoms are subtle but are due to such serious conditions as cervicomedullary compressive syndromes, syringomyelia or hydrocephalus; thus, the early identification of this disorder is very important. We made a prospective study of 39 patients (20 female, 19 male) with ACh; their ages ranged from 3 months to 17 years (mean 4 years and 6 months). All patients had hypotonia and psychomotor delay; 3 had recurrent apnea, 1 developed radicular syndrome and 1 had leg paresthesias. The CT scan was normal in 5, 20 had cortical atrophy and 18 communicating hydrocephalus; we identified foramen magnum abnormalities in 28 patients, and reduced craniocervical junction with cervicomedullary compression in 6. Myelography and myelotomography demonstrated spinal compression in 12 patients. The MRI showed cervicomedullary infarct in 1, syringomyelia in 2 and diastematomyelia in 1. The somatosensory evoked responses (SSER) were very useful in the early identification of brain stem and spinal abnormalities. We concluded that the neurological manifestations of pediatric patients with ACh are frequent and very important, demanding comprehensive clinical evaluation even in asymptomatic patients, especially those with severe hypotonia or SSER alterations.